The Characteristics Of Reservoirs And Hydrocarbon Accumulation In The Middle Section Of The Steep Slope Zone In Chezhen Depression

Dawangbei area is located in the central of CheZhen depression,and its area is 100 Km~2.During the deposition of Shahejie formation,multiple types of glutenite fans were formed.Because of sedimentary environment and diagenetic evolution,favorable reservoirs distribution is unclear with strong reservoirs heterogeneity and reservoir-forming rule is complex which is restricting exploration in the area.To solve the above problems,theories and technologies of sequence stratigraphy,sedimentology,reservoir geology and Petroleum Geology are used to study the characteristics of reservoirs and hydrocarbon accumulation in the Steep slope zone systematically.Results show:during the deposition of the Shahejie formation,there are three main types of sedimentary facies(fan delta,neritic subaqueous fan and turbidite fan),nine subfacis and more than 10 microfacies.By combining logs and seismic data,fans of different period are described and macroscopic distribution of reservoirs is clear.According to observation and analysis of rock slice,rock types,reservoir space types and porosity evolution of different layers are studied.Then diagenetic evolution was studied.Compaction,cementation,dissolution and metasomatism could be recognized from Shahejie formation which mainly belongs to stage A of middle diagenesis phase.The diagenesis evolution models of different lithic fragment types are builded.Based on this,It discusses specially parent rock's control on the development of favorable reservoirs.Combined with the study of sedimentary facies and formation pressure,favorable reservoirs are predicted.According the anatomy of typical reservoirs,hydrocarbon enrichment differences in the study area are definite.Thus analyze the main controlling factors hydrocarbon accumulations of respectively deep and shallow layers,and build 3 reservoirs forming modes:high pressure-very low porosity-autochthonous type,medium pressure-low porosity-autochthonous type and normal pressure-higher porosity-allochthonous type.Finally,based on the systematic study of sedimentary reservoir characteristics and hydrocarbon accumulation,and under the guidance of the main control factors and accumulation patterns of reservoirs,with current exploration results,the favorable exploration targets are predicted and evaluated.